Introduction to MongoDB
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An introduction to MongoDB as shown at the Madison MongoDB User Group (MadMUG) meetup on 4/16/2012.
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Introduction to MongoDB
- 1. StudyBlue Introduction to MongoDB Sean Laurent April 16, 2012 StudyBlue, Inc.
- 2. Overview • NoSQL landscape • MongoDB features • Availability & Scalability • Useful Tools • Strengths & Weaknesses StudyBlue, Inc.
- 3. Who am I? • Sean Laurent • sean@studyblue.com • Director of Operations at StudyBlue, Inc. StudyBlue, Inc.
- 5. About StudyBlue • Bottom-up attempt to improve student outcomes • Online service for storing, studying, sharing and ultimately mastering course material • Digital backpack for students StudyBlue, Inc.
- 6. StudyBlue Usage • Many simultaneous users • Rapid growth • Cyclical usage StudyBlue, Inc.
- 9. NoSQL Data Models • Key-Value stores • Document stores • Column-oriented databases • Graph databases StudyBlue, Inc.
- 10. Key-Value Stores • Maps keys to values • Operations: • Get, Set and Delete • Examples: • Cassandra, Project Voldemort, memcache, Redis StudyBlue, Inc.
- 11. Document Stores • Contains “documents” • Documents have “fields” • Secondary indexes • Operations: • Insert, Update, Delete, Update fields • Examples: • MongoDB, CouchDB StudyBlue, Inc.
- 12. Column Oriented Databases • Reversed relational database • Data for column kept together • Operations: • Insert, Update, Delete; update fields • Examples: • BigTable, HBase, CStore, Greenplum StudyBlue, Inc.
- 13. Graph Databases • Stores edges between nodes • Operations: • Getting/Setting edges • Annotate vertices or edges • Query for paths • Examples: • GraphBase, Neo4j, VertexDB StudyBlue, Inc.
- 15. Document Oriented • System holds databases • A database holds collections • A collection holds documents • A document is a set of fields written in JSON • A field is key-value pair • A key is a string • A value is a basic type, an array or another document StudyBlue, Inc.
- 16. Sample Document { “author” : “sean”, “title” : “Intro to MongoDB”, “tags” : [ “mongodb”, “introduction” ], “views” : 42, “comments” : [ { “author” : “bob”, “comment” : “Best presentation EVER!” }, { “author” : “tom”, “comment” : “Way too long winded.” } ] } StudyBlue, Inc.
- 17. Flexible Schemas • Different documents in one collection can have different fields: { “author” : “sean”, “title” : “Intro to MongoDB” } { “author” : “sean”, “title” : “Databases At Scale”, “tags” : [ “mongodb”, “scaling” ] } StudyBlue, Inc.
- 18. Query Features • No joins • No transactions across documents or collections • Atomic updates • Simple query syntax StudyBlue, Inc.
- 19. Query Examples db.posts.find({author: ‘sean’}) db.posts.find({author: ‘sean’}).sort({timestamp: 1}) db.posts.find({author: ‘sean’}).sort({timestamp: 1}).limit(2) db.posts.find({author: ‘sean’, tags: ‘mongodb’}) db.posts.find({author: ‘sean’, tags: {$in: [‘mongodb’, ‘intro’]}}) db.posts.find({author: ‘sean’, views: {$gt: 10}}) db.posts.find({$or: [{author: ‘sean’}, {views: ${gt: 20}]}) db.posts.find({}, {author: 1, views: 1}) StudyBlue, Inc.
- 20. Update Examples db.posts.update({author: ‘sean’}, { $incr: {views: 1}}) db.posts.update({author: ‘sean’}, { $set: {views: 350}}) db.posts.update({author: ‘sean’}, { $push: {tags: ‘awesome’}}) db.posts.update({author: ‘sean’}, { $set: {views: 350}}, /* upsert */ true) db.posts.update({author: ‘sean’}, { $incr: {views: 1}}, /* upsert */ false, /* multi */ true) StudyBlue, Inc.
- 21. Indexes • B-Tree indexes • Embedded fields • Compound keys • Sparse • Unique • v2.1.0 or later support background indexing StudyBlue, Inc.
- 22. Official Drivers • C • C++ • Erlang • Haskell • Java • Javascript • .NET (C#, F#, PowerShell) • Perl • PHP • Python • Ruby • Scala StudyBlue, Inc.
- 23. Community Supported Drivers • ActionScript 3 • Clojure • Dart • Go • Groovy • node.js • Objective C • Rails 3 • ... StudyBlue, Inc.
- 24. Other Cool Stuff • Aggregation • Explain • Map Reduce • Capped collections • GridFS • Geospatial indexing StudyBlue, Inc.
- 26. Replication • Replica sets • Asynchronous master/slave replication • Consists of two or more nodes that are copies of each other • Eventual consistency • Automatic failover • Automatically elects a primary (aka master) • Automatic recovery StudyBlue, Inc.
- 27. Replica Set Benefits • Redundancy / Disaster Recovery • Automated failover • Read scaling • Maintenance StudyBlue, Inc.
- 28. Replica Set - Read Scaling StudyBlue, Inc.
- 29. Replica Set Elections • Consensus Vote • Arbiters • Priorities • By default, all nodes have equal priority • Assign custom priorities for more powerful machines or specific datacenters • Highest priority amongst the most up-to-date nodes will be elected StudyBlue, Inc.
- 30. Sharding • Horizontal scaling (write scaling) • Automatic data partitioning & balancing • Automatic query routing • Each shard is typically a replica set • Sharding is enabled per collection StudyBlue, Inc.
- 31. Shards • Shard keys define partitions • Names one or more fields that determine how the data is distributed • Order preserving - adjacent data (by key) tend to be stored on the same server • Chunks • Contiguous range of data from a particular collection • Chunks grow to a maximum size, then split into two new chunks • Automatically migrates chunks when chunk count is sufficiently imbalanced between different shards StudyBlue, Inc.
- 33. Sharding Pieces • Config servers (mongoc) • Stores cluster metadata • Data about each shard and the chunks on that shard • Two-phased commits • Routing servers (mongos) • Receives client requests and routes to appropriate server(s) • Pulls state from config servers • Lightweight - run anywhere (including application servers) StudyBlue, Inc.
- 35. Useful Tools • mongo shell • mongostat • mongotop • Mongo Monitoring Service (MMS) StudyBlue, Inc.
- 36. mongo shell • Interactive Javascript shell • Part of the MongoDB installation • Issue commands & queries: ./bin/mongo mydatabase type “help” for help > db mydatabase > person = db.people.findOne( { name : "sara" } ); > person.city = "New York"; > db.people.save( person ); StudyBlue, Inc.
- 37. mongostat • View statistics on a running mongod instance StudyBlue, Inc.
- 38. mongotop • Track the amount of time a MongoDB instance spends reading and writing data on a per collection basis StudyBlue, Inc.
- 39. MMS • Free, cloud-based monitoring service • Charts • Dashboards • Automated alerting • http://mms.10gen.com StudyBlue, Inc.
- 41. Good At • Horizontal scaling • High availability • Rapidly evolving schemas StudyBlue, Inc.
- 42. Less Good At • Drop-in replacement for existing SQL RDBMS • Highly transactional operations (e.g. OLTP) • Ad-hoc business intelligence • Durability without replica sets • Automatic sharding != perfect data distribution StudyBlue, Inc.
- 44. Contact us Web: http://www.studyblue.com Twitter: @StudyBlue Email: sean@studyblue.com Twitter: @organicveggie StudyBlue, Inc.
Hinweis der Redaktion
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- - Developer at heart\n- 15 years experience\n- Responsible for selecting Mongo\n\n
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- - Bottom-up attempt to improve student outcomes through disruptive change outside of the education system. \n- Allows students to create and store lecture notes and flashcards and access them online and via mobile apps (iOS and Android)\n
- - No public numbers\n- Thousands of simultaneous users at peak\n
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- Also called “non-relational databases”\n
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- update() defaults to updating ~only~ the first matching document unless “multi” is set to true.\n
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